As I was skimming through Wikipedia about Marathon (Just downloaded it), I came across the W'rkncacnter.

A piece of terminal text from M:Durandal said this:"In primordial space, timeless creatures made waves. These waves created us and the others. Waves were the battles, and the battles were waves. "Fleeing all W'rkncacnter, Yrro and Pthia settled upon Lh'owon." Pthia & Yrro; Librarian & Didact. Librarian stayed on Earth, away from the Flood. The Didact lived in the Ark, also away from the Flood (debatable)."They brought the S'pht, servants who began to shape the deserts of Lh'owon into marsh and sea, rivers and forests."
The various constructs they made, such as Sentinels & Constructors. Lh'owon could be a Halo, or a terraformed planet, or something else. "They made sisters for Lh'owon to protect and maintain the paradise." The other Halos and Installations."When the W'rkncacnter came, Pthia was killed, and Yrro in anger, flung the W'rkncacnter into the sun. The sun burned them, but they swam on its surface." The activation of the Halos.
Remember that the Halos worked by starving The Infection. So, in a way(by killing the sentient Gravemind, or the starvation itself), the Sun(Halos) burned them, but they swam on its surface (The Flood survived the original pulse, but died from Starvation).

Also, it said in Infinity that a W'rkncacnter was imprisoned on the Sun. Like the Flood in Installation 04 (and 05).
The Pfhor used a trih xeem device to send the star into early nova, and the creature was released, to the horror and destruction of the Pfhor.
The Covenant tricked(or simply didn't know about the Flood) the humans into opening the Chamber which contained the Flood, and most of the Covies in Installation 05 perished when the Parasite was released, to their horror.